1. Field of the Invention
This invention relates to plasticizers. In one aspect the invention relates to plasticizers derived from bio-sources while in another aspect, the invention relates to plasticizers derived from microorganisms such as bacteria and algae. In yet another aspect the invention relates to plasticizers derived from genetically modified microorganisms while in still another aspect, the invention relates to compositions comprising such a plasticizer and a polar polymeric resin.
2. Description of the Related Art
Plasticizers are compounds or mixtures of compounds that are added to polymer resins to impart softness and flexibility. Phthalic acid diesters (also known as “phthalates”) are well-known petroleum-derived plasticizers that are widely used in many flexible polymer products, such as polymer products formed from polyvinyl chloride (PVC) and other polar polymers. Known petroleum-derived plasticizers also include trimellitates and adipic polyesters both typically used in high temperature applications. Mixtures of plasticizers are often used to obtain optimum properties.
Petroleum-derived plasticizers, particularly the phthalate plasticizers, however have come under intense scrutiny by public interest groups that are concerned about their negative environmental impact and potential adverse health effects in humans (especially children). As such, plasticizers derived from other sources have become of great interest, particularly those derived from seeds and nuts. Exemplary sources include but are not limited to oils derived from soy bean, linseed, tung seed, coconut, palm, olive, cotton seed, oiticica seed and castor bean. One example of such a plasticizer is soy-derived epoxy fatty acid methyl ester or e-FAME. Plasticizers derived from seed and nut sources have proved effective but here too, they come with problems.
One such problem is that these plant-derived plasticizers are mixtures of a number of different compounds not all of which are necessary or beneficial to the function of plasticizing. For example, soy oil comprises palmitic, stearic, oleic, linoleic, linolenic and higher molecular weight (more carbon atoms) fatty acids only some of which can be converted to a methyl ester and the double bonds epoxidized to make e-FAME. Palmitic and stearic acids are saturated, i.e., are without double bonds, and as such, they cannot be epoxidized. These saturated fatty acid esters have very low solubility in PVC and other polar vinyl polymers, and they tend to precipitate out of the liquid plasticizer on standing at ambient temperature (23° C.). Fatty acids with 22 or more carbon atoms, even with multiple double bonds and after epoxidation, also exhibit solubility issues.
Another problem with the use of seed- and nut-derived plasticizers is they divert the use of these materials from dietary uses, and this imparts upward pressure on the costs of many food products.